The present invention relates to a method of pasteurizing a flow of a liquid product consisting of beer, milk, milk products, fruit juice, fruit juice products or similar consumable liquids, the amount of such liquid product to be pasteurized being at least around 1,000 l/hr.
In connection with heat treating such liquid products to eliminate the bacterial content thereof, a measure of the effectiveness of the heat treatment or pasteurization is the uptake of Pasteurizing Units, PU's. The uptake of PU's is a function of the temperature of the liquid product and the time period in which the liquid product is at a temperature at which PU's are taken up.
It is essential for most applications that a minimum number of PU's be taken up, but on the other hand over-pasteurization should not happen as it will be detrimental to the quality of the pasteurized product.
Many pasteurizing methods and apparatus have a heat exchanger for heating the product up to a certain pasteurizing temperature at which the product is maintained for a period of time. Two conventional types of such apparatus are described in the following in connection with FIGS. 1 and 2 in the accompanying drawings. These known pasteurizers, as well as the pasteurizer disclosed in U.S. Pat. No. 4,997,662, have a holding tube in which the liquid product flows at a certain temperature to which it has been heated before entering the holding pipe.
In case of an anomaly in the operation of the pasteurizer such as a stoppage or a sharp decrease in flow rate of the product, the product in the holding pipe is subjected to over-pasteurization or under-pasteurization so that it has to be discarded. A by-pass can be established or water can substitute the product until normal operation is obtained again.